Solid state light sources (LEDs, light emitting diodes) have been paid much attention for many years. Since LEDs have many advantages, such as small volume, low power consumption, long lifetime, fast-response, environmental friendliness, high reliability, etc., they are widely used as components in decorating lamps, indicating lamps, etc. According to recent developments, it is possible for LEDs to be advanced into the general lighting field.
As for current LED technologies, white LEDs are recommended to generate by packaging blue LED and phosphors. In U.S. Pat. No. 5,998,925, Nichia achieved the white-light LED by combining (RE1-rSmr)3(Al1-s,Gas)5O12 yellow phosphor with GaInN blue-light LED. Then, Osram developed (Tb1-x-yRExCey)3(Al,Ga)5O12 phosphor for LEDs in U.S. Pat. No. 6,669,866. In 2002, General Research Institute for Nonferrous Metals and Grirem Advanced Materials Co., Ltd made public that the luminous intensity can be improved by coactivation mode in patent CN1482208 (general formula, R(3-x-y)M5O12:CexR′y). It is thought by the General Electric Company in U.S. Pat. No. 6,409,938 that the quantum efficiency and emission intensity of aluminate phosphor are far away from goals, and they could be improved when O2− is partly substituted by F−.
However, our research results show that bivalent metal element can be introduced to improve the quantum efficiency and emission intensity. The bivalent metal element partly substitutes Al3+ or Y3+ of the phosphor, and can compensate for the charge center formed by F− substituting O2−, which can promote the light conversion efficiency and improve the stability of this phosphor.
In this invention, the inventors present an aluminate phosphor by co-doped with bivalent metal element and fluorine. This phosphor has a broad excitation range, which can be excited by ultraviolet, purple or blue light, and exhibits high luminous efficiency and good stability. On the other hand, a light emitting device incorporating this phosphor is also concerned.